Process for the production of printed circuits with solder rejecting sub-zones

Claim 1

In a process for the production of a printed circuit board having first sub-zones of a wiring pattern for receiving solder and second sub-zones provided with a solder rejecting property so that they do not receive solder, said process including providing a workpiece comprising a substrate with a conductive metal layer on at least one surface, etching each of the layers to form the desired wiring pattern, the improvement comprising prior to the step of etching, applying a positively acting photo layer on each of the conductive metal layers, subjecting each of the photo layers to a first exposure and development process to expose the first sub-zones of each of the conductive metal layers, then galvanically applying a solderable, etch-resistant metal layer onto the exposed first sub-zones of each of the conductive metal layers, subsequently subjecting each of the photo layers to a second exposure and development process to produce an etching mask of a pattern of the second sub-zones on each of the conductive metal layers, and subsequent to the etching step, removing each of the etching masks from the second sub-zones and dipping the workpiece in an aqueous solution of liver of sulfur to form a passivation layer with a solder rejection property on each of exposed second sub-zones without impairing the solderability of the etch-resistant metal layer of the first sub-zone.